New method for gradient extraction, separation and recovery of iron, vanadium and titanium from vanadium-titanium marine placer

Abstract

The invention discloses a novel method for gradient extraction and separation recovery of iron, vanadium and titanium from vanadium-titanium marine placer, which comprises the following steps: uniformly mixing a vanadium-titanium marine placer raw material, an oxalic acid solution, reduced iron powder and deionized water, carrying out hydrothermal complexing leaching reaction to realize efficient leaching of iron, vanadium and titanium elements, and carrying out centrifugal separation to obtain a ferrous oxalate product; and carrying out hydrothermal reduction precipitation reaction on the leachate A to obtain a titanium dioxide product, adding V2O3 seed crystal into the leachate B as a crystal nucleus, and carrying out hydrothermal induction precipitation crystallization to obtain a vanadium trioxide product so as to realize gradient recovery of vanadium and titanium components. According to the method, high-purity and high-added-value ferrous oxalate, TiO2 and V2O3 are prepared aiming at the problems of cost and environment confronted by vanadium-titanium marine placer utilization, the defects that a traditional low-grade vanadium-titanium resource treatment process is complex, high in energy consumption and high in smelting cost are overcome, the process is simple, environment friendliness is achieved, the added value of products is high, social benefits and economic benefits are remarkable, and the method is suitable for industrial production. Good application prospects are realized.

Description

Technical Field

[0001] This invention relates to the field of metallurgical and chemical technology, specifically to a process for extracting, separating, and recovering iron, vanadium, and titanium from vanadium-titanium sea sand ore. Background Technology

[0002] Marine sand deposits are complex iron ore resources found in coastal areas, primarily formed by the erosion of waves, rivers, tides, and ocean currents. They are characterized by titanium magnetite as the main mineral phase and are widely recognized in the industry as low-grade vanadium-titanium magnetite resources that are difficult to process, beneficiate, and smelt. The main phases are magnetite (Fe3O4), ilmenite (FeTiO3), ilmenite spinel (Fe2TiO4), magnesia spinel (MgFe2O4), and fir olivine (Fe2SiO4). Ilmenite and iron are closely interdependent, and simple physical beneficiation methods cannot effectively separate the vanadium, titanium, and iron components. Marine sand ore has a dense structure, complex intermingling of valuable metallic minerals, and regular shapes, mostly spherical or elliptical. It has a smooth, dense surface, and relatively coarse grain size, averaging about 100-150 μm, with particles larger than 70-80 μm accounting for about 95%. It has high hardness and melting point. Compared to other iron ores, it has a smaller specific surface area, poorer hydrophilicity, and inferior ball milling and pelletizing properties, significantly limiting its use in blast furnace smelting of ordinary iron ore. The total iron content of marine sand ore is generally around 60%, with a titanium content of about 7-9%. It also contains minerals that are difficult to sinter, including relatively high amounts of Al₂O₃, K₂O, and Na₂O. Furthermore, during blast furnace smelting, the intermingling of TiO₂ increases the TiO₂ content in the blast furnace slag, thus affecting its flowability. Therefore, the large-scale utilization of vanadium-titanium marine sand ore currently faces many challenges.

[0003] To achieve comprehensive utilization of marine sand resources, scholars both domestically and internationally have conducted extensive research. The article "New Processing Technology for Vanadium-Titanium Marine Sand Ore," published in the first issue of *Modern Metallurgy* in 2015, not only introduced blast furnace and non-blast furnace methods for processing vanadium-titanium marine sand ore, but also studied a new processing technology. The vanadium-titanium marine sand ore from the raw material processing stage undergoes grinding, drying, roller milling, batching, mixing, and pelletizing. It then enters a chain grate-rotary kiln-annular cooler for drying, roasting, and cooling. The cooled vanadium-titanium oxide pellets are used as raw materials for the hydrogen vertical shaft furnace reduction process. The high-temperature metallized pellets from the hydrogen vertical shaft furnace reduction process enter a melting electric furnace, where they are melted and separated into titanium slag and vanadium-containing molten iron through arc heating and resistance heating. The vanadium-containing molten iron is then transported to a vanadium-blown converter for refining into vanadium slag and high-quality molten iron for sale. The new process produces titanium slag, vanadium slag, and high-quality molten iron, with titanium slag grade >55% and vanadium slag grade >20%, all of which can be used as raw materials for subsequent vanadium-titanium deep processing, achieving comprehensive recovery and utilization of vanadium, titanium, and iron resources in vanadium-titanium sea sand mines. However, this new process is essentially still a pyrometallurgical technology, which has high energy consumption, and the grades of titanium slag and vanadium slag are still relatively low, resulting in low added value of the products, requiring further deep processing.

[0004] Chinese patent application "A method for sintering sea sand ore (CN 20231009857.9)" involves adding binders, fluxes, coal powder, and adhesive powder to vanadium-titanium sea sand ore, and then adding the sea sand ore and other iron-bearing ore mixture to a sintering trolley for sintering. However, this method does not adjust the raw material characteristics of the sea sand ore, and the amount added is only 7-10%, making it difficult to achieve large-scale resource utilization. Patent "A carbon-containing pellet of vanadium-titanium sea sand ore and its preparation method (CN201910436076.1)" uses bituminous coal, ordinary vanadium iron ore, and vanadium-titanium sea sand ore as raw materials, and heats, presses, and heat-treats the mixture to finally prepare hot-pressed carbon-containing pellets with a compressive strength of over 3000N. This process can further increase the proportion of vanadium-titanium sea sand ore added, but the increase is limited and cannot fundamentally solve the dilemma of large-scale utilization of sea sand ore. The process is complex and long, and the added value of the product is not high, so it has not been widely used in industry. The patent "A method for producing vanadium-titanium alloy steel from sea sand ore and laterite nickel ore (CN 201710258704.2)" proposes an alloy material with certain corrosion resistance, strength, hardness and wear resistance as basic raw materials, providing another idea for the comprehensive utilization of sea sand ore. However, the product has many types and high content of impurities, and the smelting conditions are harsh, which limits the development and application of this alloy steel. In general, current research on the comprehensive utilization of sea sand as a raw material for ironmaking mainly focuses on optimizing the basic properties, metallization rate, and reducibility of sea sand when adding it to sinter. However, the amount added is small, making it difficult to achieve large-scale utilization of sea sand. There are still no reports on how to cleanly and efficiently extract valuable elements from sea sand to prepare high-value-added products and achieve large-scale, resource-based, and high-value utilization. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing vanadium-titanium sea sand ore processing technologies, such as high energy consumption, low titanium and vanadium slag grades, low product added value, and complex, long process flow that makes it difficult to achieve large-scale utilization of sea sand ore. The invention provides a new method for the tiered extraction and separation of iron, vanadium, and titanium from vanadium-titanium sea sand ore, which is simple in process, environmentally friendly, and produces products with high added value.

[0006] To achieve the above-mentioned objectives of this invention, the method of this invention uses marine magnetite as raw material and oxalic acid as leaching and capturing agent. Under pre-designed conditions and parameters such as temperature, pressure, time, liquid-solid ratio, oxalic acid concentration, and stirring speed, the valuable components such as iron, vanadium, and titanium enriched in marine magnetite are utilized in a tiered, efficient, and high-value manner, ultimately transforming them into high-purity ferrous oxalate, vanadium oxide, and titanium oxide. The specific processing approach is as follows: First, using hydrothermal complexation leaching and hydrothermal reduction precipitation, the iron present in the sea sand is reconstructed and enriched into high-value-added ferrous oxalate. At this time, the iron in the sea sand precipitates into ferrous oxalate, while titanium and vanadium exist in the leachate in the form of soluble complex ions. Using the leachate obtained from the above operation as raw material, and taking advantage of the difference in solubility of vanadium and titanium complex ions under hydrothermal conditions, the Ti and V in the leachate are finally converted into TiO2 and V2O3 by using pressure heating leaching and hydrothermal induced crystallization, thus realizing the tiered and high-value utilization of valuable components in vanadium-titanium sea sand.

[0007] This invention discloses a novel method for the cascade extraction and separation recovery of iron, vanadium, and titanium from vanadium-titanium sea sand ore, which is implemented according to the following process and steps:

[0008] S1 Hydrothermal Complexation Simultaneous Leaching of Iron, Vanadium, and Titanium

[0009] Vanadium-titanium sea sand ore raw material, oxalic acid solution, reduced iron powder, and deionized water are thoroughly mixed according to a set ratio to form a uniform slurry. The slurry is then added to a reaction vessel and sealed. Subsequently, the vessel is placed in a heating device, and the reaction temperature, reaction time, and stirring speed are controlled to carry out a hydrothermal complexation leaching reaction. The reaction products are ferrous oxalate, titanium-containing oxalate complex ions, vanadium-containing oxalate complex ions, and a solid-liquid mixture of leaching residue. The particle size of the vanadium-titanium sea sand ore raw material is 100-500 mesh, the mass concentration of the oxalic acid solution is 5-30%, the liquid-solid ratio of the oxalic acid solution to the vanadium-titanium sea sand ore raw material is 5:1-30:1 mL / g, the amount of reduced iron powder added is 0.5-5% of the mass of the vanadium-titanium sea sand ore, and the reaction vessel temperature is 90-180 ℃.

[0010] S2 Centrifugal Separation and Recovery of High-Purity Ferrous Oxalate

[0011] After the reaction in step S1 is completed, the solid-liquid mixture in the reactor is removed. Utilizing the density difference between ferrous oxalate and the leaching residue, the solid-liquid mixture is separated by centrifugation. The leaching tailings are discharged, yielding ferrous oxalate product. The ferrous oxalate product is then placed in a vacuum drying oven for dehydration to obtain ferrous oxalate powder with a Fe recovery rate of over 90% and a FeC2O4 purity of ≥95.0%. The leachate A obtained after solid-liquid separation is used as raw material for subsequent step-by-step separation and recovery of TiO2 and V2O3.

[0012] S3 Pressure heating reaction to prepare high-purity TiO2

[0013] The leachate A obtained in step S2 was placed in a reaction vessel and then sealed. Taking advantage of the characteristic that titanium oxalate complex ions are easily precipitated under reducing environment and pressure heating, a hydrothermal reduction precipitation reaction was carried out. The hydrothermal temperature was 140~190 ℃ and the pressure heating reaction time was 2~8 h. After the reaction was completed, the reaction product in the reaction vessel was taken out and subjected to solid-liquid separation. The leachate B obtained after solid-liquid separation was used as the raw material for subsequent vanadium extraction. The solid phase product obtained from solid-liquid separation was filtered, washed and dried to obtain titanium dioxide product with Ti recovery rate of over 99% and TiO2 purity ≥ 95.0%.

[0014] Preparation of high-purity V2O3 by hydrothermal induced crystallization using S4

[0015] V₂O₃ seeds were added to the leachate B obtained in step S3 as crystal nuclei. The pH of leachate B was adjusted, and vanadium-containing oxalate complex ions in leachate B were precipitated by hydrothermal induction precipitation crystallization to obtain V₂O₃ crystal precipitate. After the reaction was completed, the reaction product in the reactor was taken out and subjected to solid-liquid separation. The reaction tail liquid was recycled as a solvent for subsequent repeated leaching of vanadium-titanium sea sand. The solid product obtained from solid-liquid separation was filtered, washed, and dried to obtain vanadium trioxide product with a V recovery rate of over 95% and a V₂O₃ purity of ≥95.0%.

[0016] Preferably, in step S1, the particle size of the vanadium-titanium sea sand ore raw material is controlled in the range of 200-300 mesh, and the mass concentration of the oxalic acid solution is controlled in the range of 15-20%; the liquid-solid ratio of the oxalic acid solution to the vanadium-titanium sea sand ore raw material is 10:1-20:1 mL / g, the amount of reduced iron powder added is 1-3% of the mass of the vanadium-titanium sea sand ore, the temperature of the reactor is 120-150 ℃, the reaction time is controlled in the range of 3-10 h, preferably 4-8 h; and the stirring speed is controlled in the range of 200-500 r / min, preferably 300-400 r / min.

[0017] Preferably, in step S2, the rotation speed of the centrifugal separator is 1500~3000 r / min, preferably 2000~2500 r / min; the drying temperature of the vacuum drying oven is 60~95 ​​℃, preferably 70~80 ℃; the drying time is more than 6 h, preferably 10~12 h; and the vacuum degree is controlled at -0.3~0 MPa, preferably -0.2~-0.1 MPa.

[0018] Preferably, in step S3, the hydrothermal temperature is controlled within the range of 170~180 ℃, and the pressure heating reaction time is controlled within 5~6 h.

[0019] Preferably, in step S3, the drying is carried out in a vacuum drying oven for 10-12 hours, at a temperature of 70-80°C, and with the vacuum level adjusted to -0.2 to -0.1 MPa.

[0020] Preferably, in step S4, the pH of the solution is adjusted to the range of 1.5 to 2.5 by adding H3PO4 / NaH2PO4 to the leachate B; the amount of V2O3 seed crystals added to the leachate B is 2 to 20 g / L; the hydrothermal reaction temperature for hydrothermal induced precipitation crystallization is 100 to 200 °C, and the hydrothermal reaction time is 2 to 10 h.

[0021] Furthermore, in step S4, the hydrothermal reaction temperature for hydrothermal induced precipitation crystallization is controlled within the range of 120~150 ℃, and the hydrothermal reaction time is controlled within the range of 4~6 h.

[0022] Furthermore, in step S4, drying is carried out in a vacuum drying oven for 10-12 hours at a temperature of 70-80 °C and with the vacuum level adjusted to -0.2 to -0.1 MPa.

[0023] The method of this invention, employing the above technical solution, completely abandons the traditional pyrometallurgical treatment of sea sand ore, instead using it as a blending process for sintering and pelletizing. It features mild reaction conditions, simple equipment, and high recovery rates, enabling the comprehensive extraction and high-value utilization of iron, vanadium, and titanium. Furthermore, compared to traditional pyrometallurgical processes that can only recover vanadium and titanium resources individually, the method provided in this invention can achieve one-step co-leaching of iron, vanadium, and titanium components, followed by stepwise and graded recovery. This avoids mutual interference between different components, resulting in lower energy consumption, lower emissions, and greater environmental friendliness, while also producing higher added value, demonstrating significant social and economic benefits.

[0024] Compared with existing technologies, the novel method for the cascade extraction and separation recovery of iron, vanadium, and titanium from vanadium-titanium sea sand ore of this invention has the following innovations and beneficial effects:

[0025] (1) Compared with conventional low-grade vanadium-titanium resource comprehensive utilization technology, the present invention provides a new method for the cascade extraction and separation and recovery of iron, vanadium and titanium from vanadium-titanium sea sand, which achieves efficient "co-extraction" of iron, vanadium and titanium components. The recovery rate of Ti can reach more than 99%, the recovery rate of V can reach more than 95%, and the recovery rate of Fe can reach more than 90%.

[0026] (2) The method of this invention achieves the stepwise separation and recovery of different components through hydrothermal reduction precipitation, centrifugal separation, and seed-induced crystallization precipitation. The final FeC2O4, TiO2, and V2O3 products all have a purity of over 95% and do not affect each other. Traditional processes usually use pyrometallurgical treatment of sea sand magnetite, which requires small amounts of additives and results in low added value. Based on the market price of the products, this invention can increase profits by 5 to 8 times compared to traditional processes.

[0027] (3) Compared with the traditional pyrometallurgical process, the new process proposed in this invention eliminates a series of lengthy pretreatment processes such as crushing, mixing, and pelletizing, making the process simpler; the equipment used are all common leaching equipment, without involving high temperature and high pressure devices, resulting in lower equipment investment costs and significantly reducing production costs by about 30-50%; the amount of wastewater and waste residue generated is greatly reduced, resulting in significant economic benefits.

[0028] (4) The method of the present invention overcomes the problems of long process flow, high temperature, high energy consumption, large emissions and easy environmental pollution of traditional pyrometallurgical process. According to the process flow provided by the method of the present invention, oxalic acid is used as the leaching agent, avoiding the use of strong acid and strong alkali. The waste liquid disposal is simpler and more in line with environmental protection requirements. It is a technology that enterprises urgently need and has significant social and environmental benefits. Attached Figure Description

[0029] Figure 1 The principle process flow diagram of a new method for the cascade extraction and separation recovery of iron, vanadium, and titanium from vanadium-titanium sea sands provided by this invention;

[0030] Figure 2 The XRD pattern of the vanadium-titanium sea sand ore raw material processed in the embodiment of the method of the present invention is shown. Cu-Kα target radiation was used, the diffraction angle 2θ was 10~90°, and the X-ray wavelength λ=0.15416 nm.

[0031] Figure 3 Macroscopic morphology diagram of vanadium-titanium sea sand ore raw material processed in an embodiment of the method of the present invention;

[0032] Figure 4 Microscopic morphology diagram of vanadium-titanium sea sand ore raw material processed in an embodiment of the method of the present invention;

[0033] Figure 5 The XRD pattern of the ferrous oxalate product prepared by the hydrothermal complexation precipitation reaction of the present invention is shown. Cu-Kα target radiation was used, with a diffraction angle 2θ of 10~90° and X-ray wavelength λ=0.15416 nm.

[0034] Figure 6The XRD pattern of TiO2 prepared by the pressure heating reaction of the present invention is shown. Cu-Kα target radiation was used, the diffraction angle 2θ was 10~90°, and the X-ray wavelength λ=0.15416 nm.

[0035] Figure 7 This is a curve showing the effect of the amount of V2O3 seed crystals added on the degree of vanadium precipitation in the method of the present invention;

[0036] Figure 8 This is a graph showing the effect of hydrothermal time on the degree of vanadium precipitation in the method of the present invention.

[0037] Figure 9 The XRD pattern of high-purity V2O3 prepared by hydrothermal induced crystallization according to the method of the present invention is shown. Cu-Kα target radiation was used, the diffraction angle 2θ was 10~90°, and the X-ray wavelength λ=0.15416 nm. Detailed Implementation

[0038] To further describe the present invention, the following detailed description, in conjunction with the accompanying drawings and embodiments, provides a novel method for the cascade extraction and separation recovery of iron, vanadium, and titanium from vanadium-titanium sea sand ore.

[0039] In this embodiment, the vanadium-titanium sea sand raw material comes from the vanadium-titanium sea sand mine on the coast of New Zealand. It is a complex iron ore resource with titanomagnetite as the main mineral phase, formed by river, wave, and tidal erosion. It is also recognized worldwide as a difficult-to-process and difficult-to-smelt vanadium-titanium magnetite resource. The main phases include magnetite (Fe3O4), ilmenite (FeTiO3), ilmenite spinel (Fe2TiO4), magnesia spinel (MgFe2O4), and falconite (Fe2SiO4), etc. The total iron content is about 60%, the titanium content is about 7-9%, and it also contains high levels of Al2O3, K2O, Na2O and other minerals that are difficult to sinter. Sea sand ore particles are regular in shape, mostly spherical or elliptical, with smooth and dense surfaces, relatively coarse particle size, and high hardness and melting point. Compared with other iron ores, it has a small specific surface area, poor hydrophilicity, and poor ball milling and pelletizing performance, which greatly limits its use in blast furnace smelting of ordinary iron ore. However, the amount added is not high, with a maximum of only 15-20%.

[0040] First, the vanadium-titanium marine magnetite raw material was subjected to XRF and chemical analysis for component analysis. The results are shown in Tables 1 and 2.

[0041] Table 1 Chemical composition of experimental raw materials (mass percentage / %)

[0042]

[0043] Table 2. Analysis of the content of major valuable elements Fe, V, and Ti in the experimental raw materials (mass percentage / %)

[0044]

[0045] The results above show that the total iron content of the sea sand used in the experiment was 57.56%. In addition, the sea sand also contained other valuable components, such as Ti and V, with contents of 4.36% and 0.29% respectively. The phase analysis results of the raw materials are as follows: Figure 2 As shown: This sea sand deposit is mainly composed of hematite, magnetite and ilmenite spinel. Titanium is mainly present in the sea sand deposit in the form of ilmenite spinel, while vanadium is mainly present in the magnetite in the form of isomorphous substitution of Fe in Fe3O4.

[0046] Macroscopic morphological characteristics of marine magnetite sands, such as Figure 3 As shown, Figure 4 This is a microscopic morphology diagram of marine sand deposits. (From...) Figure 3 and Figure 4 The characterization results show that the sea sand particles are relatively regular in shape, exhibiting obvious spherical or ellipsoidal shapes. The particles are smooth and glossy, with a high density, which is not conducive to pelletizing.

[0047] The particle size distribution of the raw materials was analyzed using a laser particle size analyzer. The results showed that the marine sand ore had a relatively coarse particle size, with particles smaller than 101.086 μm accounting for only 10%. The specific particle size distribution is shown in Table 3.

[0048] Table 3 Particle size composition of marine sand raw materials

[0049]

[0050] Table 4 Specific surface area of ​​marine sand raw materials

[0051]

[0052] The specific surface area of ​​the marine sand ore was analyzed using the nitrogen adsorption BET method, and the results are shown in Table 4. The table shows that the specific surface area of ​​this marine sand ore is much lower than that of ordinary vanadium-titanium magnetite powder, which is the main reason why it is difficult to pelletize and is widely used in blast furnace feed ore blending.

[0053] Depend on Figure 1 The principle process flow diagram of the new method for the cascade extraction and separation recovery of iron, vanadium, and titanium from vanadium-titanium sea sand ore provided by this invention shows that the method of this invention is implemented through the following process steps:

[0054] S1 Hydrothermal Complexation Simultaneous Leaching of Iron, Vanadium, and Titanium

[0055] Vanadium-titanium sea sand ore raw material, oxalic acid solution, reduced iron powder, and deionized water are thoroughly mixed according to a set ratio to form a homogeneous slurry. The slurry is then added to a reaction vessel, which is subsequently sealed. The vessel is then placed in a heating device, and the reaction temperature, reaction time, and stirring speed are controlled to carry out a hydrothermal complexation leaching reaction. The reaction products are ferrous oxalate, titanium-containing oxalate complex ions, vanadium-containing oxalate complex ions, and a solid-liquid mixture of leaching residue, namely FeC2O4 and [Ti(C2O4)3]. 3- [V(C2O4)3] 3- Composite solution.

[0056] S2 Centrifugal Separation and Recovery of High-Purity Ferrous Oxalate

[0057] After the reaction in step S1 is completed, the solid-liquid mixture in the reactor is removed. Taking advantage of the density difference between ferrous oxalate and the leaching residue, the solid-liquid mixture is separated by centrifugation. The leaching tail residue is discharged to obtain ferrous oxalate product. The ferrous oxalate product is placed in a vacuum drying oven for dehydration to obtain ferrous oxalate powder product. The leachate A obtained after solid-liquid separation is used as the raw material for subsequent step-by-step separation and recovery of TiO2 and V2O3.

[0058] S3 Pressure heating reaction to prepare high-purity TiO2

[0059] The leachate A obtained in step S2 was placed in a reaction vessel and then sealed. Taking advantage of the characteristic that titanium oxalate complex ions are easily precipitated under reducing environment and pressure heating, a hydrothermal reduction precipitation reaction was carried out. After the reaction was completed, the reaction product in the reaction vessel was taken out and subjected to solid-liquid separation. The leachate B obtained after solid-liquid separation was used as the raw material for subsequent separation and extraction of vanadium. The solid phase product obtained from solid-liquid separation was filtered, washed and dried to obtain titanium dioxide product.

[0060] Preparation of high-purity V2O3 by hydrothermal induced crystallization using S4

[0061] V₂O₃ seeds were added to the leachate B obtained in step S3 as crystal nuclei. The pH of leachate B was adjusted, and vanadium-containing oxalate complex ions in leachate B were precipitated by hydrothermal induction precipitation crystallization to obtain V₂O₃ crystal precipitate. After the reaction was completed, the reaction product in the reactor was taken out and subjected to solid-liquid separation. The reaction tail liquid was recycled as a solvent for subsequent repeated leaching of vanadium-titanium sea sand. The solid product obtained from solid-liquid separation was filtered, washed, and dried to obtain vanadium trioxide product.

[0062] In this embodiment, the hydrothermal complexation of precipitated iron and the preparation of ferrous oxalate were carried out in a magnetically stirred reactor. Sea sand, deionized water, oxalic acid, and reduced iron powder were thoroughly mixed and added to the magnetically stirred reactor. After sealing the autoclave, the hydrothermal complexation of precipitated iron to prepare ferrous oxalate was initiated under the set reaction temperature, reaction time, and stirring speed. The analysis results of Fe, Ti, and V before and after the reaction are shown in Table 5 when the leaching temperature is 135 ℃, the oxalic acid concentration is 25%, the liquid-to-solid ratio is 10 mL / g, the reaction time is 90 min, and the iron powder addition is 3%. After the reaction, the autoclave was cooled to room temperature in air. The slurry was separated and recovered from the ferrous oxalate using a centrifuge at 2000 r / min for 1 h. Finally, the separated ferrous oxalate and tailings were dried in an oven at 70 ℃ for 12 h under a vacuum of -0.1 MPa.

[0063] Table 5. Contents of Fe, Ti, and V in marine sand deposits before and after the reaction.

[0064]

[0065] The reaction products were then analyzed by XRD, and the results are as follows: Figure 5 As shown: the ferrous oxalate prepared by the reaction has a good crystal form, matches well with the ferrous oxalate standard card, and has a low content of impurity components; the XRF analysis results of the product are shown in Table 6; the purity was determined by potassium permanganate titration and was 98.36%.

[0066] Table 6. Chemical composition of the experimentally prepared ferrous oxalate (mass percentage / %)

[0067]

[0068] The leachate obtained in the previous step was used as raw material, and the contents of Fe, Ti, and V are shown in Table 7. The reaction equipment was the magnetically stirred reactor described above. The pressure heating reaction temperature was 170 ℃, and the reaction time was 6 h. The analysis results of Fe, Ti, and V in the leachate after the pressure heating reaction to prepare TiO2 are shown in Table 7: the Ti content decreased from 1530 mg / L to 1.07 mg / L, and the conversion rate reached over 99%; the V content changed from 114 mg / L to 102 mg / L, and since it did not participate in the reaction, its concentration remained essentially unchanged. After the reaction, the autoclave was cooled to room temperature in air, and TiO2 was separated and recovered by filtration. Finally, the separated ferrous oxalate and tailings were dried in an oven at 70 ℃ for 12 h under a vacuum of -0.1 MPa. The XRD analysis results of the precipitate are shown in Table 7. Figure 6As shown, under the pressure-heat reaction conditions of 170 °C and a reaction time of 90 min, the Ti in the leachate almost completely reacts to form TiO2 with good crystallinity.

[0069] Table 7. Fe, Ti, and V composition of leachate before and after TiO2 preparation via pressure heating reaction

[0070]

[0071] The Ti content and other impurity element content in the separated TiO2 were quantitatively analyzed by ICP, and the results are shown in Table 8. As can be seen from the table, the purity of the TiO2 product is approximately 98.18%.

[0072] Table 8. Content of major elements in high-purity TiO2 products prepared by pressure heating precipitation

[0073]

[0074] The leachate obtained in the previous step was used as the raw material for preparing V₂O₃. V₂O₃ seed crystals were added as nuclei, and the pH of the solution was adjusted. Vanadium-containing oxalate complex ions present in the solution were precipitated using an induced crystallization method, resulting in the precipitation of V₂O₃ crystals. The effects of the amount of V₂O₃ added and the reaction time on the vanadium precipitation reaction were studied. The experimental conditions were: hydrothermal temperature 180 ℃, reaction time 24 h, and stirring speed 500 rpm. When the amount of V₂O₃ seed crystals added was 5 g / L, the vanadium precipitation degree reached 98.69%.

[0075] Figure 7 This is a graph showing the effect of the amount of V₂O₃ seed crystals added on the degree of vanadium precipitation in the method of this invention. Experiments showed that when the hydrothermal time increased from 1 h to 6 h, the degree of vanadium precipitation increased from 94.37% to 97.24%; however, when the hydrothermal reaction time was further increased to 24 h, the degree of vanadium precipitation only increased to 98.32%. After the reaction, the autoclave was cooled to room temperature in air, and V₂O₃ was separated and recovered by filtration. Finally, the separated product was dried in an oven at 70 ℃ for 12 h under a vacuum of -0.1 MPa.

[0076] Under optimal conditions—a V₂O₃ addition of 10 g / L, a reaction time of 6 h, and a hydrothermal temperature of 180 ℃—the vanadium precipitation degree was greater than 98.3%. Furthermore, the composition of the V₂O₃ product obtained under these optimal conditions was determined by ICP, and the results are shown in Table 9. As can be seen from the table, the purity of the V₂O₃ product is approximately 95.5%.

[0077] Table 9. Content of major elements in high-purity V2O3 products prepared by hydrothermal induced crystallization

[0078]

[0079] It should be noted that the iron, vanadium, and titanium contents in vanadium-titanium sea sand raw materials vary, and the process conditions need to be adjusted accordingly. For example, the liquid-to-solid ratio of oxalic acid solution to vanadium-titanium sea sand ore raw material and the ratio of reduced iron powder added in step S1, and the amount of V2O3 seed crystals added in step S4, etc. However, inspired by the technical solution and embodiments of this invention, by appropriately adjusting the process parameters, a Ti recovery rate of over 99%, a V recovery rate of over 95%, and an Fe recovery rate of over 90% can ultimately be obtained, and the purity of the final FeC2O4, TiO2, and V2O3 products can all reach over 95%.

[0080] Compared with traditional pyrometallurgical processes that can only recover vanadium and titanium resources individually, the method provided in this invention can achieve the "one-step" synergistic leaching of iron, vanadium, and titanium components, followed by step-by-step and graded recovery. This avoids the mutual influence between different components, resulting in lower energy consumption, fewer emissions, and greater environmental friendliness, while also increasing the added value of the products and demonstrating significant social and economic benefits.

Claims

1. A novel method for the cascade extraction and separation recovery of iron, vanadium, and titanium from vanadium-titanium sea sand ore, characterized in that... The following steps are adopted: S1 hydrothermal complexation and simultaneous leaching of iron, vanadium, and titanium; Vanadium-titanium sea sand ore raw material, oxalic acid solution, reduced iron powder, and deionized water are thoroughly mixed according to a set ratio to form a uniform slurry. The slurry is then added to a reaction vessel and sealed. Subsequently, the vessel is placed in a heating device, and the reaction temperature, reaction time, and stirring speed are controlled to carry out a hydrothermal complexation leaching reaction. The reaction products are ferrous oxalate, titanium-containing oxalate complex ions, vanadium-containing oxalate complex ions, and a solid-liquid mixture of leaching residue. The particle size of the vanadium-titanium sea sand ore raw material is 100-500 mesh, the mass concentration of the oxalic acid solution is 5-30%, the liquid-solid ratio of the oxalic acid solution to the vanadium-titanium sea sand ore raw material is 5:1-30:1 mL / g, the amount of reduced iron powder added is 0.5-5% of the mass of the vanadium-titanium sea sand ore, and the reaction vessel temperature is 90-180 ℃. S2 Centrifugal separation and recovery of high-purity ferrous oxalate; After the reaction in step S1 is completed, the solid-liquid mixture in the reactor is removed. Utilizing the density difference between ferrous oxalate and the leaching residue, the solid-liquid mixture is separated by centrifugation. The leaching tailings are discharged, yielding ferrous oxalate product. The ferrous oxalate product is then placed in a vacuum drying oven for dehydration to obtain ferrous oxalate powder with a Fe recovery rate of over 90% and a FeC2O4 purity of ≥95.0%. The leachate A obtained after solid-liquid separation is used as raw material for subsequent step-by-step separation and recovery of TiO2 and V2O3. S3 Pressure heating reaction to prepare high-purity TiO 2； The leachate A obtained in step S2 was placed in a reaction vessel and then sealed. Taking advantage of the characteristic that titanium oxalate complex ions are easily precipitated under reducing environment and pressure heating, a hydrothermal reduction precipitation reaction was carried out. The hydrothermal temperature was 140~190 ℃ and the pressure heating reaction time was 2~8 h. After the reaction was completed, the reaction product in the reaction vessel was taken out and subjected to solid-liquid separation. The leachate B obtained after solid-liquid separation was used as the raw material for subsequent vanadium extraction. The solid phase product obtained from solid-liquid separation was filtered, washed and dried to obtain titanium dioxide product with Ti recovery rate of over 99% and TiO2 purity ≥ 95.0%. Preparation of high-purity V2O by hydrothermal induced crystallization using S4 3； V₂O₃ seeds were added to the leachate B obtained in step S3 as crystal nuclei. The pH of leachate B was adjusted, and vanadium-containing oxalate complex ions in leachate B were precipitated by hydrothermal induction precipitation crystallization to obtain V₂O₃ crystal precipitate. After the reaction was completed, the reaction product in the reactor was taken out and subjected to solid-liquid separation. The reaction tail liquid was recycled as a solvent for subsequent repeated leaching of vanadium-titanium sea sand. The solid product obtained from solid-liquid separation was filtered, washed, and dried to obtain vanadium trioxide product with a V recovery rate of over 95% and a V₂O₃ purity of ≥95.0%.

2. A novel method for the cascade extraction and separation recovery of iron, vanadium, and titanium from vanadium-titanium marine sands as described in claim 1, characterized in that: In step S1, the particle size of the vanadium-titanium sea sand ore raw material is controlled in the range of 200-300 mesh, and the mass concentration of the oxalic acid solution is controlled in the range of 15-20%; the liquid-solid ratio of the oxalic acid solution to the vanadium-titanium sea sand ore raw material is 10:1-20:1 mL / g, the amount of reduced iron powder added is 1-3% of the mass of the vanadium-titanium sea sand ore, the temperature of the reactor is 120-150 ℃, the reaction time is controlled in the range of 3-10 h, and the stirring speed is controlled in the range of 200-500 r / min.

3. A novel method for the cascade extraction and separation recovery of iron, vanadium, and titanium from vanadium-titanium marine sand ore as described in claim 2, characterized in that: In step S1, the reaction time is controlled within the range of 4 to 8 hours, and the stirring speed is controlled within the range of 300 to 400 r / min.

4. A novel method for the cascade extraction and separation recovery of iron, vanadium, and titanium from vanadium-titanium marine sand deposits as described in claims 1, 2, or 3, characterized in that: In step S2, the rotation speed of the centrifugal separator is 1500~3000 r / min; the drying temperature of the vacuum drying oven is 60~95 ​​℃, the drying time is more than 6 h, and the vacuum degree is controlled at -0.3~0 MPa.

5. A novel method for the cascade extraction and separation recovery of iron, vanadium, and titanium from vanadium-titanium sea sand as described in claim 4, characterized in that: In step S2, the centrifugal separator rotates at a speed of 2000~2500 r / min; the vacuum drying oven is dried at a temperature of 70~80 ℃ for 10~12 h, and the vacuum degree is controlled at -0.2~-0.1 MPa.

6. A novel method for the cascade extraction and separation recovery of iron, vanadium, and titanium from vanadium-titanium sea sand as described in claim 5, characterized in that: In step S3, the hydrothermal temperature is controlled within the range of 170~180 ℃, and the pressure heating reaction time is controlled within 5~6 h.

7. A novel method for the cascade extraction and separation recovery of iron, vanadium, and titanium from vanadium-titanium marine sand ore as described in claim 6, characterized in that: In step S3, drying is carried out in a vacuum drying oven for 10-12 hours at a temperature of 70-80°C and with the vacuum level adjusted to -0.2-0.1 MPa.

8. A novel method for the cascade extraction and separation recovery of iron, vanadium, and titanium from vanadium-titanium sea sand as described in claim 7, characterized in that: In step S4, the pH of the solution is adjusted to the range of 1.5 to 2.5 by adding H3PO4 / NaH2PO4 to leachate B; the amount of V2O3 seed crystals added to leachate B is 2 to 20 g / L; the hydrothermal reaction temperature for hydrothermal induced precipitation crystallization is 100 to 200℃, and the hydrothermal reaction time is 2 to 10 h.

9. A novel method for the cascade extraction and separation recovery of iron, vanadium, and titanium from vanadium-titanium marine sand ore as described in claim 8, characterized in that: In step S4, the hydrothermal reaction temperature for hydrothermal induction of precipitation crystallization is controlled in the range of 120~150 ℃, and the hydrothermal reaction time is controlled in the range of 4~6 h.

10. A novel method for the cascade extraction and separation recovery of iron, vanadium, and titanium from vanadium-titanium marine sand ore as described in claim 9, characterized in that: In step S4, drying is carried out in a vacuum drying oven for 10-12 hours at a temperature of 70-80 °C and with the vacuum level adjusted to -0.2-0.1 MPa.

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